diff options
Diffstat (limited to '18/a.lua')
-rw-r--r-- | 18/a.lua | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/18/a.lua b/18/a.lua new file mode 100644 index 0000000..b9dd2d1 --- /dev/null +++ b/18/a.lua @@ -0,0 +1,55 @@ +input = io.lines('input.txt') + +function is_op(token) + return token == '+' or token == '*' +end + +function f_op(op) + if op == '+' then + return function (a, b) return a + b end + else + return function (a, b) return a * b end + end +end + +function is_digit(token) + return token >= '1' and token <= '9' +end + +function do_math(expression) + stack = {} + for i = 1, #expression do + token = expression:sub(i, i) + if is_op(token) then + table.insert(stack, token) + elseif is_digit(token) then + if is_op(stack[#stack]) then + op = table.remove(stack) + n = table.remove(stack) + table.insert(stack, f_op(op)(n, tonumber(token))) + else + table.insert(stack, tonumber(token)) + end + elseif token == '(' then + table.insert(stack, token) + elseif token == ')' then + res = table.remove(stack) + table.remove(stack) + if is_op(stack[#stack]) then + op = table.remove(stack) + n = table.remove(stack) + table.insert(stack, f_op(op)(n, res)) + else + table.insert(stack, res) + end + end + end + return stack[1] +end + +sum = 0 +for line in input do + sum = sum + do_math(line) +end + +print(sum) |